I currently have my gems at lvl 16 and I do > 4k fire damage on hit with a 50% chance to ignite.
Kole burns down with one trap if ignited. I expect the damage to more than double with maxed gems.
€: Now I'm almost at 8K fire on hit.

Gear
Core items are:

As you see 'core items' are actually, besides Blackgleam and (optional) Windscreams only those gems, which are

The first four gems are a must. Culling Strike, Fire Penetration and Increased Burning Damage can be swapped on a 5l. A Cold to Fire gem could also be considered when running Hatred.
I only use the bow for the +1 gem levels, a 5l chest would also be possible, I used a crappy one until today. I lved this build with Tabula Rasa which works well until a3m. I'd suggest a hybrid ar/es chest.
Blackgleam gives a huge conversion to fire damage, Searing Touch by far does not work as well.
The rest of my gear isn't endgame or lategame yet, I just wanted to try out this idea and it works really really well and makes quite some fun. It's a pretty 'active' build I'd say. :)

Gameplay
I use 1-2 totems to group mobs, cast 0-3 curses beeing Elemental Weakness, Flammability, Vulnerability and throw 1-3 traps into that group. On ignite (50% chance) the group burns down in about 1 sec, any magic and rares burn down aswell.
The area of elemental proliferation is huge, ranged mobs attacking the totems will poof aswell.

Defense
I have arctic armour running and Discipline, Clarity, Grace and Hatred. I'll add determination and might switch Hatred to Purity if possible. I have one more hotkey slot left for a defensive curse - Temporal Chains could be considered because it would also increase the burning duration.

Passive Skill Tree
My passive tree looks like this.
My next points will go into life and armour/es.
Price Tag
I use some expensive quality gems and also Blackgleam and that bow didn't come cheap.
I expect this build to work with any 5l armour and any average Blackgleam and Windscreams though. With non quality gems and mid rolled items this build would 'cost' a few GcPs.
A downside of this build is that you need quite high stats in int, str and dex, which might make you squichy with missing life or resis on your gear. Still with some caution it should be very playable and doesn't really rely on any expensive items.

Summing Up
This build was kind of meant to be a fun build on my second Path of Exile char.
It turned out to be really nice to play though, with incredibly high dps, crowd control and (probably) the ability to play endgame maps. It's a great support for groups with it's 3 curses and 5 auras, but actually you won't just be 'their' sidekick - they will be yours! ;)

Any constructive criticism, advice and suggestions on skills, items and so on are very welcome! :)
(ig @Chiinto)

nice :D i use bear trap with added fire ele prolif and chance to ignite on my trapster to be able to have something replacing the lost fire traps from the patch.Its cool to see someone make a build around that :P

oh and that green socket can be pretty useful for the multiple traps support gems thats gonna come out :D

Nice idea.
With the upcoming trap patch i would replace culling strike with that new trap support gem. Culling strike is a little bit wasted here as it will only work with the initial damage not the burning damage. Burning damage is considered dot afaik not hit, therefore culling strike won't apply.

nice :D i use bear trap with added fire ele prolif and chance to ignite on my trapster to be able to have something replacing the lost fire traps from the patch.Its cool to see someone make a build around that :P

oh and that green socket can be pretty useful for the multiple traps support gems thats gonna come out :D

Nice idea.
With the upcoming trap patch i would replace culling strike with that new trap support gem. Culling strike is a little bit wasted here as it will only work with the initial damage not the burning damage. Burning damage is considered dot afaik not hit, therefore culling strike won't apply.

Ty. Burning damage depends on fire damage on hit dealt and Culling Strike actually does increase the fire damage, but not too much though. That 3% on lvl 1 give me about 50 more fire damage. :)

and it would be really awesome if you could post some gameplay vids later on. As a stranger to trapper builds, i'd like to see your build in action especially on maps.

Ty :) Yeah I'll try to do so, I'm currently on a slow laptop unfortunately, not sure if it will work on this system..

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Any advice or suggestions on items apart from those 3 mentioned above are very appreciated.
I'm currently having some resistance problems. The reason probably is that I rely too much on str/dex gear. I got really basic equip for my rings, body armour and helmet. I'm might go for AH to support 2 % reserving auras.